WO2018139758A1

WO2018139758A1 - System for drying lignite and method for drying lignite

Info

Publication number: WO2018139758A1
Application number: PCT/KR2017/014728
Authority: WO
Inventors: 이주선
Original assignee: 이주선
Priority date: 2017-01-24
Filing date: 2017-12-14
Publication date: 2018-08-02
Also published as: US10941984B2; EP3575382A1; US20180209738A1; EP3575382A4; AU2017396357A1; KR101761319B1; AU2017396357B2; EP3575382B1; CN108387069A

Abstract

A system for drying lignite, according to the present invention, comprises: a grinder for grinding low rank lignite containing a large amount of water; a drier for drying the ground lignite by means of high-temperature steam and discharging the same; a condensation dust collection evaporator for condensing, through heat exchange with water, the saturated steam to be evaporated and discharged during the drying of the lignite in the drier, and collecting the coal dust, having been generated during the drying of the lignite, in an aqueous solution containing condensed saturated steam, and discharging the same; and an evaporated steam recompressor compressing the steam evaporated by the condensation dust collection evaporator so as to supply the same to the drier.

Description

Lignite drying system and lignite drying method

The present invention relates to a low grade coal drying system including lignite, and more particularly, to recycling steam generated during the drying of low grade coal and steam generated by heat exchange with steam generated from low grade coal. A method of supplying a recompressor and a dryer relates to a lignite drying system having improved thermal efficiency.

Recently, due to disasters, refrain from using nuclear power plants, and interest in existing power plants such as thermal power plants is increasing.

Coal-fired power plants generally use coal, which is a huge deposit on Earth. Coal, which is used as the main fuel of steam power plants, requires low moisture content. When the moisture content in the coal is low, the calorific value is low, the combustion efficiency is lowered due to the amount of heat consumed to evaporate moisture during combustion, there is a problem that the cost of transporting the coal also increases.

Lignite, which is classified as low coal in coal, has high water content and low calorie, low thermal efficiency when used in thermal power plants, and low economic efficiency due to high CO ₂ and SO ₂ emission problems. Also causes.

In coal-fired power plants, the design is based on low moisture content coal, so dehydration must be carried out in order to use low-grade coal such as lignite. Accordingly, techniques for reducing moisture content by drying low quality coal having a high moisture content such as lignite are known.

As one example, there is a technique of drying the lignite by supplying hot heated air inside the transfer pipe while transferring the lignite in the transfer pipe. Such a technology has a problem that a safety accident occurs when fired coal and air come into contact.

As another example, a technique is known for supplying superheated vapor to remove moisture from the lignite surface. Superheated steam is directly in contact with lignite to remove moisture, so the efficiency of removing water is low, and considering the cost of operating a separate device to continuously supply the superheated steam, there is a problem of low efficiency.

In addition, a technique using a fluidized bed dryer using the residual heat of the exhaust gas of the boiler and the exhaust steam of the low pressure turbine has been developed, but there is a limitation in reducing the residual heat by evaporating moisture due to insufficient heat or temperature.

In addition, lignite generates harmful substances during drying, so there is a problem in that environmentally hazardous substances must be properly disposed.

The present invention aims to dry lignite with high efficiency by recycling steam generated during drying of lignite.

In particular, the purpose of using steam generated from lignite as a heat source for generating steam supplied to the dryer and as a heat source for preheating the lignite supplied to the dryer and as a sweep gas to help smoothly discharge saturated steam from the dryer It is done.

In addition, an object of the present invention is to efficiently process coal and harmful substances generated during the drying of lignite.

In addition, an object of the present invention is to generate and circulate the steam used in the dryer inside the system.

The object is to supply a crusher for pulverizing lignite, a lignite pulverized from the crusher, a dryer for drying the lignite by the heat exchange with steam to discharge the dried lignite, and to supply steam evaporated and discharged during the lignite drying And a condensing dust evaporator which communicates with the dryer so as to condense the steam discharged from the dryer by heat exchange with water, and collects the coal dust contained in the steam in the condensed aqueous solution, and discharges the condensed aqueous solution. It is achieved by the lignite drying system, characterized in that it receives a steam generated from, and comprises an evaporation steam material compressor for compressing the steam to the superheated steam to supply to the dryer.

A portion of the steam exiting the dryer may be supplied to the dryer as a sweep gas.

The system of the present invention may further include a centrifugal separator for receiving the condensed aqueous solution from the condensation dust evaporator and separating the aqueous solution from the coal.

The system of the present invention may further include a preheater that receives the sensible heat of the separated aqueous solution separated by the centrifuge, and heats the lignite discharged from the grinder to preheat the lignite.

The system of the present invention may further include a blower for pressurizing the steam supplied to the condensation dust evaporator.

The system of the present invention may further include a heat exchanger receiving a portion of the superheated steam compressed by the evaporation steam recompressor and exchanging the superheated steam supplied with the steam discharged from the dryer to convert the steam into superheated steam. Can be.

The steam supplied to the dryer is discharged as hot water, and the system of the present invention may further include a reduced pressure evaporator for receiving hot water discharged from the dryer and evaporating the hot water to steam to supply the evaporation steam material compressor. .

The dryer has an inlet through which lignite is introduced, an outlet through which dried lignite is discharged, a steam outlet through which steam generated when the lignite is dried, an overheated steam inlet through which sweep gas is introduced, and steam are passed through the dryer. A plurality of hollow shafts arranged in parallel to the plurality of disks, a plurality of disks installed on the hollow shaft to rotate to transport the supplied lignite to the outlet, and paddles attached to the disks; The plurality of disks may be arranged at predetermined intervals such that the disks of the other shaft are disposed between the disks of one of the shafts.

The condensation dust evaporator is supplied with one or more steam conduits through which the steam discharged from the dryer passes, and water that heat-exchanges to condense the steam in the steam conduits, surrounding the steam conduits on an outer wall, and by evaporation of water. It may include a shell for discharging the generated steam.

In addition, the present invention, a method for drying lignite, pulverized lignite and supplying to the dryer; Drying the lignite supplied to the dryer by heat exchange with steam; Supplying steam generated when the lignite is dried to a condensation dust evaporator, condensing the supplied steam by heat exchange with water, and collecting dust included in the steam when the steam is condensed; And converting steam evaporated from water through the heat exchange into an overheat steam by compressing the steam evaporated from the water into an evaporation steam recompressor, and supplying the overheat steam to the dryer.

The method according to the present invention may further include the step of changing the steam generated during drying of the lignite into superheated steam before pressurizing and supplying it to the dryer as a sweep gas.

In the method according to the present invention, the aqueous solution condensed and discharged from the condensation dust evaporator is separated into an aqueous solution and sludge using a centrifuge, and the separated aqueous solution is supplied to a preheater to preheat the crushed lignite, and the separated sludge is drier. It may further comprise the step of supplying.

The method according to the present invention may further include converting the steam into superheated steam by exchanging a part of the superheated steam compressed by the evaporation steam recompressor with the steam discharged from the dryer.

The method according to the invention may further comprise the step of evaporating the hot water discharged from the dryer to a reduced pressure evaporator, and supplying the evaporated steam to the evaporation steam recompressor.

According to the lignite drying system of the present invention, steam generated when the lignite is dried can be used as a heat source of steam supplied to the dryer.

In addition, steam generated during drying of the lignite may be used to preheat the lignite.

In addition, steam generated when the lignite is dried can be used as the sweep gas of the dryer.

In addition, by collecting the coal and harmful substances generated during the drying of lignite can reduce the environmental pollution.

In addition, except for the initial operation of the steam used in the dryer, the system itself can be generated and circulated without being supplied from the outside.

Due to the above characteristics, the present invention can operate the lignite drying system with very high energy efficiency.

1 is a view schematically showing a lignite drying system according to an embodiment of the present invention.

2 is a view for explaining the flow of steam discharged from the dryer of FIG.

FIG. 3 is a view illustrating a flow of water entering and exiting the condensation dust evaporator of FIG. 1 and steam discharged from the condensation dust evaporator.

Figure 4 is a cross-sectional view of the dryer according to an embodiment of the present invention.

Figure 5 is a longitudinal cross-sectional view of the condensation dust evaporator according to an embodiment of the present invention.

Hereinafter, the lignite drying system according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view schematically showing the overall configuration of the lignite drying system.

For reference, the process of transporting lignite is indicated by a dotted line, the process of steam generated during lignite drying is represented by a solid line, and the flow of steam supplied to the dryer is represented by two solid lines.

A low grade coal having a high moisture content such as lignite is put into the grinder 10 and pulverized. For convenience of explanation, in the present specification, lignite is selected and described as low grade coal, and it should be noted that the coal to be dried in the present invention is not limited to lignite but includes all coals corresponding to low grade coal. .

Lignite usually contains 40 to 65 wt% of water and has a particle size of 0 to 100 mm. The lignite is introduced into the grinder 10 and pulverized until the particle size becomes about 0 to 1 mm.

The pulverized lignite is put into the dryer 30 and is discharged after removing moisture.

Preferably, the lignite passing through the mill may be introduced into the dryer 30 after passing through the preheater 21 and the rotary feeder 23.

By preheater 21, the pulverized lignite can be preheated to about 80 degrees Celsius. Preferably, the heat source required for the preheater is a condensate solution discharged from the condensation evaporator 50 to be described later. Specifically, the condensate solution used in the preheater is supplied from the centrifuge 60 to be described later, about 100 degrees Celsius. Lignite may be preheated by indirect heat exchange with the condensate solution.

On the other hand, lignite is supplied to the dryer 30 via the rotary feeder 23. In this case, the rotary feeder 23 prevents the vapor evaporated in the dryer from flowing back toward the line for supplying the lignite. Rotary feeder 23 is a generally known device, so a detailed description thereof will be omitted.

Dryer 30 is a device for removing moisture from the lignite. 1 and 4, the dryer 30 has an inlet 34 through which lignite is introduced at one upper end, and an outlet 35 through which the dried lignite is discharged at the lower end of the other side. The dryer 30 also includes a plurality of rotating

hollow shafts

31, 32 installed in the housing. A plurality of disks 33 are provided in the

hollow shafts

31 and 32, and the plurality of disks 33 rotate the hollow shafts along the axis.

The plurality of

hollow shafts

31 and 32 are arranged side by side in parallel, and the plurality of disks 33b provided on the other shaft 32 are disposed between the plurality of disks 33a provided on one shaft 31, respectively. Preferably, the

discs

33a and 33b are arranged at predetermined intervals. The powdered coal (pulverized lignite) introduced into the dryer is accumulated between the

disks

33a and 33b. As the two

hollow shafts

31 and 32 and the

disks

33a and 33b rotate at different speeds, the coal powder The mixing is carried out along the axial direction (from left to right in the drawing) by a paddle attached to the disc at an appropriate angle, and finally the dried coal is discharged through the outlet 35.

The insides of the

hollow shafts

31 and 32 are designed to allow steam to pass through. Steam is supplied inside the hollow shaft at a pressure of about 4 to 6 barA. Heat is transferred to the hollow shaft and the disc through steam, and the coal dust in contact with the disc and the hollow shaft is dried by this heat. That is, the powdered coal is dried by lignite absorbing the latent heat generated as the steam condenses. Lignite is not in direct contact with steam for heat exchange, but indirect heat exchange with steam by contacting the disk and the hollow shaft through which steam passes.

In addition, the powdered coal is transported violently mixed between the

disks

33a and 33b which are reversely rotated with each other. In this process, the powdered coal is transferred to heat by contact with the surface of the disk, so that the moisture contained in the powdered coal is evaporated. And separated into steam. In the present invention, by using a plurality of disks arranged in parallel, the area for transferring heat can be increased and the powdered coal can be mixed smoothly, and the drying efficiency of the powdered coal can be greatly improved.

The two hollow shafts and the discs are each controlled by a frequency control motor, so that the time for drying the coal dust can be properly adjusted to achieve the target water removal rate.

In addition, the evaporation pressure inside the dryer 30 is preferably adjusted to exceed the atmospheric pressure. If the pressure inside the dryer 30 is equal to or lower than the atmospheric pressure, there is a risk that a safety accident may occur in which air is introduced from outside by the vacuum and ignition of powdered coal. Therefore, in order to prevent such a safety accident, it is preferable to control the pressure inside the dryer 30 to be maintained higher than atmospheric pressure.

On the other hand, in order to quickly discharge the evaporated vapor evaporated from the coal dust from the dryer, an inert gas such as nitrogen or superheated steam may be introduced into the dryer as a sweep gas. The overheated steam inlet 37 is provided in the dryer 30, and thus the overheated steam may be supplied into the dryer. By using superheated steam as the sweep gas, the stability can be ensured, and the efficiency of the system can be improved by recycling the evaporated steam discharged from the dryer as described later.

The powdered coal dried in the dryer is discharged to the outside through the discharge port 35, and the discharged coal powder may be transferred to the storage facility through the conveyor 39.

As can be seen in Figures 1 and 2, the water evaporated from the coal dust is discharged in the state of saturated steam through the steam outlet (36). Saturated vapor discharged is heated to become superheated vapor, and this superheated vapor is transferred to the condensation dust evaporator 50. In addition, a portion of the saturated steam is branched before being supplied to the condensation dust evaporator 50 and supplied to the dryer 30, it can be used as a sweep gas.

Preferably, the saturated steam discharged from the dryer passes through the heat exchanger 41 before entering the condensation dust evaporator 50. Saturated steam is heated by the heat exchanger 41, and superheated steam is obtained. As the heat source of the heat exchanger 41, an overheated steam compressed by an evaporation steam recompressor 80 (MVR; Mechanical Vapor Re-Compression) described later can be used. Indirect heat exchange can occur between saturated steam and superheated steam.

When the saturated steam becomes superheated steam by the heat exchanger 41, the superheated steam can be supplied to the condensation dust evaporator 50 without condensation during transportation. In addition, the superheated steam may be supplied to the dryer 30 when used as a sweep gas.

Also, preferably, the superheated steam is pressurized by the blower 43 before being supplied to the condensation dust evaporator 50. The blower 43 pressurizes the superheated steam appropriately so that the superheated steam becomes a pressure necessary for condensation in the condensation dust evaporator 50.

The condensation dust evaporator 50 is a device for condensing superheated steam to discharge the condensate solution.

As can be seen in FIG. 5, the condensation evaporator 50 comprises a shell 53 forming a housing and a steam conduit 51 arranged inside the shell 53. The steam conduit 51 is preferably a tube through which superheated steam passes, and the superheated steam condenses while passing through the steam conduit 51 and is discharged as a condensate solution.

The shell 53 is supplied with separate water through the inlet 55, and a part of the water is evaporated through heat exchange with the steam conduit 51 and then discharged through the low pressure steam outlet 56, and the remaining water not evaporated. Is discharged through the drain 57.

That is, the water supplied into the shell 53 is in contact with the outer surface of the steam conduit 51 through which the superheated steam passes, the superheated steam is condensed while transferring heat to the water, the water in contact with the steam conduit 51 Silver becomes a low pressure steam by the latent heat of condensation generated during condensation of the superheated steam and is supplied to the evaporation steam recompressor 80 to be described later. The superheated steam passing through the steam conduit is not in direct contact with the water supplied to the shell for heat exchange, but indirectly by heat contact with the steam conduit 51 and the water.

In addition, when the superheated steam is condensed to become a condensate solution, a small amount of the solvent and the coal included in the superheated steam are included together in the condensate solution, thereby condensing the solvent and collecting dust.

In addition, the superheated steam passes through the steam conduit 51 at a high flow rate due to the pressurized air blowing of the blower 43. Due to the high flow rate of the superheated steam, the aqueous solution to be condensed and the dust collected therein can be easily discharged.

As a dust collector, an electrostatic precipitator (EST) is usually used. The efficiency is determined by the electrical resistance of contaminated dust. However, since the electrostatic precipitator has low dust collection efficiency, dust still remains in the steam discharged through the electrostatic precipitator, which may cause a failure of the system. In particular, when the steam still contains the dust is introduced into the evaporation steam recompressor (80), the dust is the main cause to interfere with the normal operation of the evaporation steam recompressor (80) or to break the evaporation steam recompressor (80) do.

Unlike the electrostatic precipitator, the condensation dust evaporator 50 of the present invention achieves an excellent cleaning effect by collecting and condensing both dust and solvent in a wet manner, and the steam supplied to the evaporation steam recompressor 80 is separate pure water. Since the evaporated steam can prevent the problem that the evaporation steam material compressor 80 is broken by the pollutant.

In other words, the superheated steam passing through the condensation dust evaporator 50 of the present invention is not supplied to the evaporation steam recompressor 80, but is condensed with the condensate solution and then supplied to the preheater 21 through a centrifuge which will be described later. The steam is fed back into the dryer together with lignite, and steam supplied from the condensation evaporator 50 to the evaporation steam recompressor 80 is generated from a separate water used to condense the superheated steam in the condensation evaporator 50. Therefore, if the electrostatic precipitator is used, there is a problem that steam containing dust is supplied to the evaporation steam recompressor. However, if the condensation precipitating evaporator of the present invention is used, there is no risk that the steam containing dust is supplied to the evaporation steam recompressor. none.

Water discharged from the condensation evaporator 50 through the drain port 57 is introduced into the condensation evaporator 50 through the pump. That is, the water used in the condensation dust evaporator 50 is circulated.

The condensate solution discharged from the condensation dust evaporator 50 includes coal dust. This condensate solution is separated into carbon and an aqueous solution through a centrifuge (60). The separated aqueous solution may be supplied to the preheater 21 as a separating aqueous solution and used to preheat the pulverized lignite. In addition, the separated coal is carried in the form of sludge, and may be introduced into the dryer 30 or the rotary feeder 23 together with the crushed lignite supplied to the dryer 30.

The centrifuge 60 may be composed of a first high speed separator and a second compression separator. The first high-speed separator separates the aqueous solution and supplies the separated aqueous solution to the preheater, and the second compression separator may supply the dewatered sludge to the rotary feeder 23. Since the configuration of the centrifuge is a general technology, a detailed description thereof will be omitted.

1 and 3, the low pressure steam discharged from the condensation dust evaporator 50 flows into the evaporation steam recompressor 80 and is compressed and discharged as an overheated steam.

Basically, the superheated steam discharged from the evaporation steam recompressor 80 is introduced into the dryer 30. On the other hand, a part of the overheated steam discharged from the evaporation steam recompressor 80 is branched to the heat exchanger 41 disposed between the dryer 30 and the condensation precipitator 50 before entering the dryer 30. Can be provided.

The heat exchanger 41 allows heat exchange between the saturated steam discharged from the dryer 30 and the superheated steam discharged from the evaporation steam recompressor 80. Through the heat exchanger 41, heat is transferred from the superheat steam discharged from the evaporation steam recompressor 80 to the saturated steam discharged from the dryer 30, whereby the saturated steam becomes superheated steam.

As such, in heating the saturated steam, by using the superheat steam from the evaporation steam recompressor without using a separate heat source, it is possible to simplify the apparatus to improve the efficiency of the apparatus and reduce the cost.

Steam condensed in the

hollow shafts

31 and 32 of the dryer 30 is discharged as hot water, which is introduced into the reduced pressure evaporator 70. The reduced pressure evaporator 70 evaporates the hot water and then introduces the evaporated steam into the evaporation steam material compressor 80. That is, the low pressure steam discharged from the condensation dust evaporator 50 is introduced into the evaporation steam recompressor 80, and the steam discharged from the reduced pressure evaporator 70 is also introduced.

The evaporation steam recompressor 80 compresses the incoming steam to a pressure required by the dryer to make the superheat steam, and then supplies the superheat steam to the dryer 30. Therefore, in the initial stage in which the dryer 30 operates, external steam is supplied to the dryer 30, but if a predetermined condition is satisfied after operating the evaporation steam recompressor 80, steam supplied from the outside is supplied. No longer in use, by directly supplying the steam discharged from the evaporation steam recompressor 80 to the dryer, it can be switched to the self-operation operation.

On the other hand, the evaporation steam recompressor 80 uses the hot water discharged from the reduced pressure evaporator 70 as cooling water in order to reduce excessive heat generated when compressing the steam, the steam is further produced by evaporation of the cooling water. This additionally produced steam can be used as a heat source of the dryer (30).

The hot water not evaporated in the reduced pressure evaporator 70 is joined to the water discharged from the condensation dust evaporator 50, flows into the condensation dust evaporator 50, and also flows into the cooling water of the evaporation steam recompressor 80.

In the following, the principle of operation of the above-described system of the present invention will be described. To help understand, first explain the process of drying lignite, the flow of steam generated during lignite drying, and then the flow of steam supplied to the dryer.

In FIG. 2, the process of drying the lignite and the flow of steam generated during lignite drying will be described. In particular, for the sake of understanding, the letters A to G are described with reference to the flow of steam.

Low grade lignite having a high water content is introduced into the grinder 10 and pulverized. The pulverized lignite is preferably preheated via the preheater 21 and then introduced into the dryer 30. By preheating before entering the dryer 30, the efficiency of evaporating moisture from the lignite can be increased. In addition, the pulverized lignite is preferably introduced into the dryer 30 through the rotary feeder 23. By using the rotary feeder 23, it is possible to block backflow of steam generated from the dryer.

The crushed lignite is put into the dryer 30 and discharged after the moisture is removed. The dried lignite is discharged through the outlet 35 and then transferred back to the lignite reservoir through the conveyor 39.

Moisture generated in the lignite during drying of the lignite is discharged through the steam outlet 36 in the form of saturated steam (see A of FIG. 2).

Saturated steam discharged through the steam outlet 36 is preferably introduced into the condensation evaporator 50 after passing through the heat exchanger 41 (see B of FIG. 2) (see FIG. 2C).

Saturated steam may receive heat from the heat exchanger 41, become superheated steam, and flow into the condensation dust evaporator 50. As such saturated steam becomes superheated steam, steam does not condense during transportation.

In addition, some of the superheated steam may be introduced into the dryer 30 (see G of FIG. 2). Part of the superheated steam flows into the dryer 30 through the superheated steam inlet 37 of the dryer 30 to serve as a sweep gas. Using superheated steam as the sweep gas can reduce the risk of explosion inside the dryer. The use of air as a sweep gas may cause a problem of ignition of powdered coal. By using superheated steam instead of air, the problem of ignition can be prevented.

In addition, the superheated steam is preferably introduced into the condensation dust evaporator 50 through the blower 43. When the superheated steam is pressurized by the blower 43, the flow rate of the superheated steam increases. As the flow rate of the superheated steam increases, the condensate solution condensed in the condensation dust evaporator 50 and the coal dust collected in the condensate solution are easily discharged.

When the superheated steam passes through the steam conduit 51 of the condensation dust evaporator 50, the superheated steam condenses while transferring heat to water in contact with the outside of the steam conduit to become a condensate solution. At the time of condensation of superheated steam, the dust and solvent contained in the superheated steam are also included in the condensate solution and discharged together with the condensate solution (see FIG. 2D).

The condensate solution discharged from the condensation dust evaporator 50 is preferably discarded and used again. To this end, the condensate solution may be separated into water and coal via a centrifuge (60). The water from which the dust is separated may be supplied to the preheater 21 as a separation aqueous solution (see E of FIG. 2). In addition, the coal separated from the condensate solution may be fed back into the dryer 30 together with lignite in the form of sludge (see F of FIG. 2).

Referring to Figure 3, it will be described in detail the flow of steam supplied to the dryer. In particular, to aid in understanding, the letter A 'to J' is described in relation to the flow of steam.

Steam supplied to the dryer 30 during the initial operation is supplied from an external source (see A 'of FIG. 3). The steam transfers heat to the

discs

33a and 33b while passing through the

hollow shafts

31 and 32 of the dryer 30 to dry the lignite in contact with the hollow shaft and the disc. Steam deprived of heat while passing through the hollow shaft is discharged into the hot water from the dryer 30 (see B 'in FIG. 3).

The discharged hot water may be supplied to the condensation dust evaporator 50 through a pump. In particular, the hot water discharged from the dryer is preferably introduced into the evaporation steam material compressor 80 after passing through the reduced pressure evaporator 70 (see C 'of FIG. 3). The reduced pressure evaporator 70 evaporates the hot water into the evaporation steam recompressor 80, and the non-evaporated hot water is transferred to the condensation evaporator 50 (see FIG. 3 'D) and the evaporation steam recompressor 80. Inflow (see J ′ in FIG. 3).

On the other hand, the condensation dust evaporator 50 is supplied with water. Water is supplied to the shell 53 of the condensation dust evaporator 50, and in contact with the steam conduit 51 disposed in the shell 53 to heat exchange. The superheated steam passing through the steam conduit 51 is condensed by performing heat exchange with water, the water absorbs the latent heat of condensation of the superheated steam, and some of the water is discharged as steam (see FIG. Is discharged as water (see I ′ in FIG. 3).

The water discharged from the condensation evaporator 50 is supplied to the condensation evaporator 50 again (see E ′ of FIG. 3). On the other hand, the water discharged from the condensation evaporator 50 is combined with the hot water discharged from the depressurization evaporator 70 to enter the condensation evaporator 50 together again (see I ', D', E 'of Figure 3). That is, the water introduced into and discharged from the condensation dust evaporator 50 circulates repeatedly. When the water to be circulated becomes insufficient, supplemental water may be additionally supplied at a predetermined point in the line through which the water is circulated (see K ′ in FIG. 3).

The low pressure steam discharged from the condensation dust evaporator 50 is supplied to the evaporation steam recompressor 80 (see F 'of FIG. 3).

The low pressure steam coming out of the condensation dust evaporator 50 and the steam coming out of the reduced pressure evaporator 70 flow into the evaporation steam recompressor 80. The evaporation steam recompressor 80 pressurizes the incoming steam and discharges it to the superheated steam (see G 'of FIG. 3). The superheated steam discharged from the evaporation steam recompressor 80 flows into the dryer 30 (see G ′ of FIG. 3). In the initial operation of the dryer 30, steam is supplied from an external source (see A ′ in FIG. 3), but if certain conditions are met, for example, if superheated steam is generated from the evaporation steam recompressor 80, The dryer 30 may be operated only by the superheat steam of the evaporation steam recompressor 80 without using steam supplied from the source.

On the other hand, a part of the superheat steam discharged from the evaporation steam recompressor 80 may be supplied to the heat exchanger 41 to be used as a heat source of the heat exchanger (see H 'of FIG. 3).

Claims

A grinder 10 for grinding lignite,

The dryer 30 receives the lignite pulverized from the crusher 10, and the lignite is dried by heat exchange with steam to discharge the dried lignite.

It is in communication with the dryer 30 so as to receive the vapor evaporated and discharged during the lignite drying, and the carbon discharged from the dryer 30 is collected by condensing the vapor discharged from the dryer 30 by heat exchange with water to condensed aqueous solution. To discharge the condensed aqueous solution, the condensation evaporator 50, and

Receiving the steam generated from the condensation evaporator (50), compresses the steam to the superheated steam to supply to the dryer 30, lignite drying system, characterized in that it comprises an evaporation steam recompressor (80).
The method of claim 1,

A part of the steam discharged from the dryer (30) is supplied to the dryer (30) as a sweep gas, lignite drying system, characterized in that.
The method of claim 1,

The lignite drying system further comprises a centrifugal separator (60) for receiving the condensed aqueous solution from the condensed dust evaporator (50) and separating the aqueous solution from the coal.
The method of claim 3,

The lignite drying system, characterized in that it further comprises a preheater (21) for receiving the separated aqueous solution separated in the centrifuge (60), heat exchange with the lignite discharged from the grinder (10) to preheat the lignite.
The method of claim 1,

Lignite drying system further comprises a blower (43) for pressurizing the steam supplied to the condensation dust evaporator (50).
The method of claim 1,

And a heat exchanger (41) which receives a portion of the superheated steam compressed by the evaporation steam recompressor and heat-exchanges the supplied superheated steam with the steam discharged from the dryer to convert the steam into superheated steam. Lignite drying system characterized in that.
The method of claim 1,

Steam supplied to the dryer 30 is discharged as hot water,

Receiving the hot water discharged from the dryer, and the evaporation steam material to evaporate the hot water to the evaporation steam material compressor (80), characterized in that it further comprises a reduced pressure evaporator (70).
The method of claim 1,

The dryer 30,

An inlet 34 through which lignite flows, an outlet 35 through which dried lignite is discharged, a steam outlet 36 through which steam generated when the lignite is dried, and an overheated steam inlet 37 through which sweep gas is introduced And a plurality of hollow shafts 31 and 32 arranged in parallel in the dryer through which steam passes, and installed on the hollow shafts 31 and 32 so as to transfer the supplied lignite to the outlet while stirring. A plurality of disks 33a, 33b having a plurality of

And the plurality of disks are arranged at predetermined intervals such that the disks of the other shaft are respectively disposed between the disks of one of the plurality of disks.
The method of claim 1,

The condensation dust evaporator 50,

One or more steam conduits 51 through which steam discharged from the dryer passes;

And a shell (53) surrounding the steam conduit, receiving a heat exchanger to condense the steam in the steam conduit, and discharging steam generated by evaporation of the water.
In the method of drying lignite,

Pulverizing lignite and feeding it to a dryer;

Drying the lignite supplied to the dryer by heat exchange with steam;

Supplying steam generated when the lignite is dried to a condensation dust evaporator, condensing the supplied steam by heat exchange with water, and collecting dust included in the steam when the steam is condensed;

Compressing the steam evaporated from the water through the heat exchange to the evaporation steam recompressor to convert to superheated steam, and supplying the superheated steam to the dryer; drying method comprising a.
The method of claim 10,

The method of drying the lignite, characterized in that further comprising the step of changing the vapor generated during the drying of the lignite into superheated steam and then pressurized air, and supplying it to the dryer as a sweep gas.
The method of claim 10,

Separating the aqueous solution condensed and discharged from the condensation dust evaporator into an aqueous solution and sludge using a centrifugal separator, and supplying the separated aqueous solution to a preheater to preheat the crushed lignite and supplying the separated sludge to a dryer. How to dry lignite characterized in that.
The method of claim 10,

And heat-exchanging a portion of the superheated steam compressed by the evaporative steam recompressor with the steam discharged from the dryer, thereby converting the steam into superheated steam.
The method of claim 10,

And evaporating the hot water discharged from the dryer to a reduced pressure evaporator to supply the evaporated steam to an evaporation steam recompressor.